Going in the "tunnel" might be difficult if you have anxiety about such spaces, but if you speak with the staff, they can help you. I know some people who get sedated.
For me the monotonous sound from within the machine causes me to sleep. I have never completed any MRI without dozing off. I saw that some newer machines have goggles and earplugs which allow you to hear and see a movie or some kind of entertainment.
If your MRI results are normal or negative, this does not mean that MS is not a possibility. Early on the initial lesion can be missed. Your MRI should include at a minimum your head and c-spine.
If you have a clear MRI and continue to present with MS like symptoms, you will most likely make a return visit to the MRI in 2-6 months unless other causes are determined.
Lyme is a real possibility too. Try to remain calm and relax because the results can take time and your doctor may want both unless something appears on your MRI to warrant further attention.